Of known melt/cast alloys, various heat-resistant alloys including Al—Cu alloys such as 2618 and other series 2000 aluminum alloys as specified in Japanese Industrial Standards (JIS) have been developed. These alloys, however, do not have sufficient strength when used at high temperatures exceeding 150° C. This is because these Al—Cu alloys ensure their strength owing to finely divided deposits formed as a result of age hardening, and the deposit phase becomes coarse to thereby reduce the strength remarkably when used at temperatures exceeding 150° C.
Aluminum based alloys prepared by rapid solidification techniques have therefore been developed. Aluminum alloys prepared by rapidly quenched powder metallurgy belonging to such rapid solidification techniques can contain larger amounts of alloy elements such as Fe, Cr, Mn, Ni, Ti, and Zr, as compared with the melt/cast aluminum alloys. Accordingly, aluminum based alloys excellent in strength even when used at high temperatures exceeding 150° C. can be obtained by powdering aluminum alloys containing large amounts of these alloy elements through rapid solidification, and compressing and molding the resulting powders (Patent Documents 1 and 2). This is because the alloy elements form dispersed particles of intermetallic compounds with aluminum in the structure, and the dispersed intermetallic compounds are stable even at high temperatures and contribute to higher strength at high temperatures.
A technique for providing high strength has been proposed, in which the fraction of such intermetallic compounds is increased by finely dividing the intermetallic compounds (Patent Document 3).
There has also been developed a lightweight heat-resistant aluminum based alloy, which further contains alloy elements such as Fe, V, Mo, Zr, and Ti, in which intermetallic compounds between these alloy elements and aluminum are finely divided by spray forming belonging to rapid solidification techniques. In addition, a high-strength aluminum based alloy with good wear resistance has been developed, in which excessive silicon (Si) is added to form finely divided silicon primary crystals (Patent Document 4).
In addition, there are also proposed a heat-resistant aluminum based alloy which is amorphous by further containing various alloy elements other than above (Patent Document 5); a heat-resistant aluminum based alloy containing a matrix and quasi-crystals uniformly dispersed in the matrix, which matrix includes a supersaturated solid solution containing two or more transition elements (Patent Document 6); and an impeller prepared by subjecting a rapidly solidified Al—Fe alloy to hot extruding and subsequently to hot forging (Patent Document 7).    Patent Document 1: Japanese Patent No. 2911708 (entire text)    Patent Document 2: Japanese Examined Patent Application Publication (JP-B) No. Hei 07-62189 (entire text)    Patent Document 3: Japanese Unexamined Patent Application Publication (JP-A) No. Hei 05-195130 (entire text)    Patent Document 4: Japanese Unexamined Patent Application Publication (JP-A) No. Hei 09-125180 (entire text)    Patent Document 5: Japanese Examined Patent Application Publication (JP-B) No. Hei 06-21326 (entire text)    Patent Document 6: Japanese Patent No. 3142659 (entire text)    Patent Document 7: Japanese Unexamined Patent Application Publication (JP-A) No. Hei 10-26002 (entire text)